In many therapeutic programs pertaining to the management of health and disease, the use of drug delivery devices that provide for the slow release of a drug to the body at a controlled rate over a prolonged period of time to achieve a desired physiologic or pharmacological effect has proved beneficial. A principal advantage of employing sustained-release compositions is that many therapeutic agents would otherwise be rapidly metabolized or cleared from the patient's system necessitating frequent administration of the drug to maintain a therapeutically effective concentration.
There has been a consistently large demand for the development of new, long-acting contraceptives that require minimal medical guidance and compliance as compared to oral contraceptives. This is particularly the case in less developed countries where medical and family planning organizations are inadequate. Accordingly, several long-acting, sustained release contraceptive delivery systems, including implants, vaginal rings, and transdermal systems have been developed. For a review, see Sitruk-Ware, et al., Contemporary Clin. Gynecol. & Obstet. 2:287-98 (2002).